1. Field of the Invention
This invention relates to mobile systems for mixing and dispensing concrete. More specifically, this invention relates to an improved fin structure for use within the mixing drums in such systems which will increase the efficiency of a system, as well as lowering maintenance and manufacturing costs.
2. Description of the Prior Art
Concrete mixing trucks such as those manufactured by the assignee of this invention, McNeilus Truck and Manufacturing Corporation of Dodge Center, Minnesota, are widely used in the construction industry for preparing and transporting a concrete mixture to a desired construction site.
A mixing truck typically includes a rotatable mixing drum which has metallic fins or agitators mounted inside for mixing and directing the movement of a concrete mixture therein. Ordinarily, such fins have a helical configuration which will tend to mix concrete when the mixing drum is rotated in a first direction, and urge the concrete toward a discharge chute when the mixing drum is turned in an opposite direction.
During operation of such trucks, a great deal of abrasive friction is generated between the mixing fins and the various abrasive components of the concrete mixture which is being transported. As a result, mixing fins typically wear out long before the outer wall of the mixing drum itself does. Accordingly, a mixing drum must either be discarded or rebuilt with new fins if it is to achieve the full extent of its own design life. Such refitting is commonly done throughout the industry, and it is a relatively expensive, time-consuming process.
Another problem with metallic fins is their tendency to oxidize or corrode, which makes them difficult to clean after use. As a result, concrete often builds up on the fins after each use. This reduces the usable volume of the drum and the efficiency of the fins during use. It also compounds the difficulty of cleaning the inside of the drum and the fins as time goes on.
Despite the above-noted problems, trucks with metallic mixing fins have been designed to operate fairly well in the past. However, it is generally recognized that the efficiency of a mixing system as a whole will be enhanced if such problems could be ameliorated.
It is clear, then, that there has existed a long and unfilled need in the art for mixing fins which have greater resistance to abrasion, which do not become roughened as they wear, and which are more lightweight than mixing fins which have been heretofore known.